In case of any Company where there is a minimum no. of Directors appointed at the time of incorporation and if any of such directors wants to resign from its post, then there is a requirement of appointment of a new director before such resignation to nullify the effect of the resignation and to avoid the circumstances where the co. will fall below the min no. .
In your case, you can do like this: first pass the resolutioon for the appointment of the new Director and then pass the resolution for the cessation of old director in the same meeting. This will automatically make ur minimum requirement fulfill. Since doing vice-versa make the company fall below the minimum no. of Directors.